Fluid dispensers are known incorporating fluid pumps in which an outer one-way check valve permits flow outwardly therepast in a downstream direction yet prevents fluid flow therepast inwardly in an upstream direction. Such known pump mechanisms include various dispensers for dispensing fluid drawn from the inside of a upstanding container for dispensing out a downwardly directed discharge outlet such as, for example, disclosed in U.S. Pat. No. 8,070,844, issued Dec. 13, 2011 to Ophardt et al, the disclosure of which is incorporated herein by reference.
Such known liquid dispensers suffer the disadvantage that after use of the dispenser, while the dispenser is at rest, fluid may drip from the discharge outlet.
Many dispensers of liquid such as hands soaps, creams, honey, ketchup and mustard and other viscous fluids which dispense fluid from a nozzle leave a drop of liquid at the end of the outlet. This can be a problem that the liquid may harden, as creating an obstruction which reduces the area for fluid flow in future dispensing. The obstruction can result in future dispensing through a small area orifice resulting in spraying in various directions such as onto a wall or user to stain the wall or user or more disadvantageously into the eyes of a user.
Many dispensers of material such as creams and for example liquid honey have the problem of stringing in which an elongate string of fluid hangs from fluid in the outlet and dangles from the outlet after dispensing an allotment of fluid. With passage of time the string may form into a droplet and drop from the outlet giving the appearance that the dispenser is leaking.
Pump assemblies for fluid dispensers are well known. Such pump assemblies includes those invented by the inventor of this present application including those disclosed in U.S. Pat. No. 5,165,577, issued Nov. 24, 1992; U.S. Pat. No. 5,282,552, issued Feb. 1, 1994; U.S. Pat. No. 5,676,277, issued Oct. 14, 1997, U.S. Pat. No. 5,975,360, issued Nov. 2, 1999, and U.S. Pat. No. 7,267,251, issued Sep. 11, 2007, the disclosures of which are incorporated herein by reference.
Many previously known piston pumps suffer the disadvantage that the pistons for the pump are difficult to manufacture.